Usually, at the mention of the word "shark", an image of a large formidable predator arises in the head, a meeting with which is dangerous for a person. However, in this superclass of cartilaginous fishes there is a unique group of truly miniature species (up to 50 cm). In the list of sharks with the smallest sizes, the second place is occupied by the dwarf (lat. Euprotomicrus bispinatus). The length of her body is only 22-27 cm, that is, the predator can be placed in the palm of your hand.
The first scientific description of the pygmy shark dates back to 1824. Currently, the species lives not only in the wild, but also at home. The diminutiveness and original appearance of Euprotomicrus bispinatus have made this predator a popular object for decorative aquarium breeding.
General characteristics
The dwarf (or pygmy) shark belongs to the Dalatian family andis the only member of the genus Euprotomicrus. The species belongs to the order katranobraznye. This taxon also includes the smallest shark in the world - Etmopterus perryi. However, Euprotomicrus bispinatus is only a couple of centimeters larger than her.
The dwarf shark is notable not only for its diminutiveness. This fish has one of the unique natural phenomena - bioluminescence. This is why Euprotomicrus bispinatus is sometimes called the pygmy luminous shark.
The animal uses the mechanism of luminescence for protective purposes. The miniature size of the pygmy shark makes it vulnerable to larger predators. The blue glow spreading along the belly has a good masking effect in the water column, as it effectively reflects light rays. This makes the shark virtually invisible to predators swimming from below. The luminescence also helps the fish to hunt. The soft shimmer is a great way to attract prey.
The maximum recorded length of a pygmy shark was 27 cm. The females of these fish are larger than the males.
Structure and appearance
The pygmy shark has a miniature dark brown (almost black) elongated conical body, tapering towards the tail. The head of this fish is very large, and the muzzle is blunt and compressed, moderately long.
The eyes of the pygmy shark are large, round and able to glow green in the dark. Behind them are sprinklers. Gill slits are very small andevenly wide. The snout accounts for 2/5 of the length of the head.
The mouth of the pygmy shark is rounded, framed by thin, fleshy lips, on which there is no fringe. The teeth on the upper and lower jaws are very different. Their structure corresponds to the features of all deep-sea sharks of the Dalatian family. The latter are characterized by the following tooth structure:
- upper - smaller, with narrow, sharp, straight tips, have a curved awl-like shape;
- lower ones are large, with a high, wide, almost vertical point, a triangular cutting edge, the bases are closed together, forming a solid blade.
The pygmy shark has all smooth teeth. On the upper jaw they are stacked in 29 rows, and on the lower jaw - in 34.
The body of Euprotomicrus bispinatus resembles a tadpole in appearance. The dorsal fins are very small, with the second being much larger than the first. They are located closer to the tail of the body.
There is no "triangle" typical for sharks on the back of this fish. The pectoral fins are rounded, and the anal fin is completely absent. The caudal fin of Euprotomicrus bispinatus differs from the heterocircal crescent-shaped structure familiar to sharks. In the pygmy, it is asymmetrical, but not lobed. The upper and lower parts are rounded and almost identical (close to the homocercal type). The subterminal notch on the fin is well developed. Precadal pits and subterminal keels on the caudal pedunclemissing.
The entire lower part of the shark's body is covered with bioluminescent organs - photophores. Their size is very small (0.3-0.8 mm), but together they give a very powerful glow. Photophores do not burn constantly, but only when the shark is in an excited state.
Habitat
The habitat of the pygmy shark is very extensive. It covers tropical and temperate waters. Within the Southeast Atlantic, this fish lives:
- near Ascension Island;
- westbound from the Cape of Good Hope;
- in the South African area;
- in the waters east of Fernando de Noronha.
Distribution in the Indian Ocean covers the open waters of Madagascar and Western Australia.
In the North Pacific, the pygmy shark inhabits the following areas:
- USA;
- Hawaiian Islands;
- Midway Island.
In the southern part of the same ocean, the distribution range covers the space between New Zealand, southern Chile and Phoenix Island.
Lifestyle
Despite its miniature size, the pygmy shark is a real predator. She preys on smaller fish, crustaceans, mollusks, and sometimes even attacks relatively large prey. In the latter case, the pygmy shark clings to the body of the victim and, making rotational movements, bites off pieces from it.
Euprotomicrus bispinatus usually hunts at night,descending in search of food to a depth of one and a half kilometers. In the daytime, this predator stays closer to the surface of the water. However, even during the day, pygmy sharks are at least 200 meters deep.
Reproduction
Euprotomicrus bispinatus reproduces by ovoviviparity. The number of cubs in the litter does not exceed 8. The body length of the born sharks is about 6 cm.
Another type of shark called "pygmy"
The pygmy spiny shark (lat. Squaliolus laticaudus) is slightly larger than the pygmy shark (body length up to 28 cm). This miniature predator is notable for the presence of a spike on the front dorsal fin, for which it received the corresponding Russian name.
The distribution area of Squaliolus laticaudus covers all oceans, except for the Arctic Ocean. However, this species is currently poorly understood.
This predator has an elongated spindle-shaped body with a long conical muzzle, on which are located large round eyes. Unlike Euprotomicrus bispinatus, the pygmy spiny shark has a pointed snout instead of a blunt one. The head of the fish is disproportionately large in relation to the body.
Miniature aquarium shark
One of the most popular modern trends in aquarism is the home keeping of sharks. Of course, only small fish are suitable for this purpose. The best choice in terms of ease of care andreservoir capacity will be miniature ornamental sharks. The latter are distinguished not only by their compactness, but also by their original appearance.
Euprotomicrus bispinatus species is ideal for the role of an aquarium. The dwarf shark is very unpretentious and tolerates captivity well. In addition, this is a very beautiful fish, the aggressiveness of which is much lower than that of larger counterparts. One of its most valuable decorative qualities is the ability to glow in the dark.
There are 4 important features to keep in mind when keeping a pygmy shark:
- correct selection of temperature;
- efficient aeration;
- sufficient volume of the aquarium (at least 200 liters).
With all the advantages of Euprotomicrus bispinatus, this ornamental predator is not a cheap pleasure. Prices for dwarf sharks for an aquarium start at 150 thousand rubles.
